A grain-oriented electrical steel sheet is mainly utilized as an iron core of a transformer and is required to exhibit superior magnetization characteristics, in particular low iron loss.
In this regard, it is important to highly accord secondary recrystallized grains of a steel sheet with (110)[001] orientation, i.e. the “Goss orientation”, and reduce impurities in a product steel sheet. Furthermore, since there are limits on controlling crystal grain orientations and reducing impurities, a technique has been developed to introduce non-uniformity into a surface of a steel sheet by physical means to subdivide the width of a magnetic domain to reduce iron loss, i.e. a magnetic domain refining technique.
For example, JP S57-2252 B2 (PTL 1) proposes a technique of irradiating a steel sheet as a finished product with a laser to introduce high-dislocation density regions into a surface layer of the steel sheet, thereby narrowing magnetic domain widths and reducing iron loss of the steel sheet. Furthermore, JP H6-072266 B2 (PTL 2) proposes a technique for controlling the magnetic domain width by means of electron beam irradiation.